A general X-ray tube uses a thermal electron source as an electron source. An X-ray tube of this type generates X-rays on the electron beam incident side by irradiating an X-ray target made of a bulk metal with thermal electrons which are emitted from a filament heated to a high temperature and spread widely. The generated X-rays are then used. A point source type X-ray tube therefore forms a pseudo point X-ray light source by obliquely extracting an elongated X-ray focus. The uniformity of an X-ray intensity distribution has been improved by spacing an X-ray light source apart from the position of an object.
Recently, a cold cathode multi electron source has been proposed as an electron source replacing this thermal electron source. In addition, as an application of this technique, a flat type multi X-ray generating apparatus with a devised method of extracting multi X-ray beams has been proposed (patent reference 1).
Furthermore, it has been proposed to use a multi X-ray source in the field of X-ray CT in which conventional point light source type X-ray tubes have been used. For example, there has been proposed a method of forming a three-dimensional CT image by measuring X-ray transmission data while rotating a combination of a multi X-ray source and a flat type two-dimensional sensor about the axis of an object and moving them along the axis (patent reference 2).